Toggle Side Panel

Shopping Cart

No products in the basket.

Shopping Cart

No products in the basket.

Close search
Home / DTC / U0249 — Lost Communication With Entertainment Control Module - Rear B

U0249 — Lost Communication With Entertainment Control Module - Rear B

Detailed page for trouble code U0249.

34,405codes
59brands
11,914generic
22,491specific
All codes P-codes (Powertrain) B-codes (Body) C-codes (Chassis) U-codes (Network/User) Tesla Alerts
Reset
Code

U0249

Generic U — Network/User

Lost Communication With Entertainment Control Module - Rear B

Brand: Generic
Type: U — Network/User
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Faulty or missing rear entertainment control module (Rear B)
  • Power or ground supply fault to the module (blown fuse, poor ground, open power feed)
  • Damaged, shorted, or disconnected data bus wiring (CAN/LIN) or connectors
  • Failed or intermittent termination resistor on the communication bus
  • Corroded or water-damaged connector at the module or in-line splice
  • Aftermarket audio/video equipment or wiring modifications interfering with the network

Symptoms

  • Rear entertainment features inoperative (audio/video, rear screens, headphones)
  • Warning or message on instrument cluster about unavailable rear entertainment
  • Multiple related network communication codes present
  • Intermittent operation of rear entertainment or sporadic fault presence
  • Other modules reporting loss of a node on the network

What to check

  • Read all stored network and communication codes; note which modules are missing from the network scan tool list
  • Verify fuses and power feed to the rear entertainment control module are present and correct
  • Inspect module connectors and wiring for corrosion, damage, pin backout, or water intrusion
  • Measure key ground(s) for low resistance to chassis (verify good ground)
  • Check CAN bus physical layer: voltage at CAN High and CAN Low with ignition ON (idle ~2.5 V each), differential behavior when bus active
  • Measure total bus termination resistance (approx. 60 ohms between CAN High and CAN Low with power off)

Signal parameters

  • CAN High idle voltage: approx. 2.5 V (can vary 2.0–3.0 V depending on system)
  • CAN Low idle voltage: approx. 2.5 V (complementary to CAN High); differential idle near 0 V, active differential ~1–2 V
  • Expected bus termination: ~60 ohms between CAN High and CAN Low (two 120 ohm terminators in parallel)
  • Typical CAN bus speeds: 500 kbps or 250 kbps (verify factory spec for vehicle)
  • LIN bus: idle close to battery voltage when awake, signal toggles between near 0 V and battery voltage
  • Module supply voltage: close to battery voltage (12 V nominal) with ignition in required position

Diagnostic algorithm

  1. Connect a capable scan tool and verify U0249 and any other communication or network codes. Note whether the Rear B module is listed or absent on the network list.
  2. Check fuses and power/ground at the rear entertainment control module connector. Repair any blown fuses or poor grounds before further testing.
  3. Visually inspect module connector(s), wiring harnesses, and any in-line junctions/splices for damage, corrosion, or water intrusion. Repair or secure connectors as needed.
  4. With ignition ON, measure CAN High and CAN Low voltages at the module connector. Compare to expected values and check for a correct differential when the bus is active.
  5. With power OFF, measure resistance between CAN High and CAN Low at two points to confirm approximate 60 ohm termination. If missing or high, locate open/failed terminator or disconnected module.
  6. If physical layer checks pass but module is still not communicating, try swapping with a known-good identical module if available, or connect the suspected module to a bench harness to verify operation.
  7. Inspect for and disconnect any aftermarket devices or headrest units that interface with the rear entertainment network; retest network communication.
  8. If wiring and power are good and replacement module is available, program/configure the replacement per manufacturer procedures. Clear codes and confirm restoration of communication and functionality.
  9. If intermittent, perform wiggle tests on harnesses while monitoring network status and consider environmental tests (heat, moisture) where applicable.
  10. If diagnostics point to a vehicle network-wide issue (multiple missing nodes, bus-off), investigate other nodes, gateway module, and possible short to battery/ground on the bus.

Likely causes

  • Open or short in CAN High/CAN Low or LIN signal wiring to rear entertainment module
  • Lost power or poor ground at the rear entertainment module connector
  • Module has failed internally or is not configured/enabled on the vehicle network
  • Damaged connector or corrosion at the rear module or junction point
  • Bus termination resistor open or incorrect value (expected ~60 ohms total)

Fault status

⚠️ Status
Lost Communication With Entertainment Control Module - Rear B (U0249). Module not responding on vehicle data bus.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.5-3.0 hours

Similar codes

U0248 U0242 U0121 U0141 U0155 U1000
8,971

The library contains 8,971 repair and diagnostic manuals. Choose a brand to open the full manual tree by year, model and trim.

ALFA ROMEO
89
AUDI
1,243
BMW
479
CADILLAC
206
CHEVROLET
456
CHRYSLER
57
DAEWOO
75
FIAT
26
GENESIS
207
HUMMER
138
HYUNDAI
371
ISUZU
86
LAND ROVER
320
LEXUS
280
LINCOLN
166
MERCEDES-BENZ
856
MERCURY
296
MITSUBISHI
406
PORSCHE
136
TESLA
58
TOYOTA
2,042
TRIUMPH
131
VOLKSWAGEN
626
VOLVO
221
Your experience will help others
+100 karma for a short comment :)
Keep it short and practical. Up to 500 characters.
Send to email
Code

U0249

HYUNDAI U — Network/User

Lost Communication With Entertainment Control Module Rear “B”

Brand: HYUNDAI
Type: U — Network/User
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Faulty or missing rear entertainment control module (Rear B)
  • Power or ground supply fault to the module (blown fuse, poor ground, open power feed)
  • Damaged, shorted, or disconnected data bus wiring (CAN/LIN) or connectors
  • Failed or intermittent termination resistor on the communication bus
  • Corroded or water-damaged connector at the module or in-line splice
  • Aftermarket audio/video equipment or wiring modifications interfering with the network

Symptoms

  • Rear entertainment features inoperative (audio/video, rear screens, headphones)
  • Warning or message on instrument cluster about unavailable rear entertainment
  • Multiple related network communication codes present
  • Intermittent operation of rear entertainment or sporadic fault presence
  • Other modules reporting loss of a node on the network

What to check

  • Read all stored network and communication codes; note which modules are missing from the network scan tool list
  • Verify fuses and power feed to the rear entertainment control module are present and correct
  • Inspect module connectors and wiring for corrosion, damage, pin backout, or water intrusion
  • Measure key ground(s) for low resistance to chassis (verify good ground)
  • Check CAN bus physical layer: voltage at CAN High and CAN Low with ignition ON (idle ~2.5 V each), differential behavior when bus active
  • Measure total bus termination resistance (approx. 60 ohms between CAN High and CAN Low with power off)

Signal parameters

  • CAN High idle voltage: approx. 2.5 V (can vary 2.0–3.0 V depending on system)
  • CAN Low idle voltage: approx. 2.5 V (complementary to CAN High); differential idle near 0 V, active differential ~1–2 V
  • Expected bus termination: ~60 ohms between CAN High and CAN Low (two 120 ohm terminators in parallel)
  • Typical CAN bus speeds: 500 kbps or 250 kbps (verify factory spec for vehicle)
  • LIN bus: idle close to battery voltage when awake, signal toggles between near 0 V and battery voltage
  • Module supply voltage: close to battery voltage (12 V nominal) with ignition in required position

Diagnostic algorithm

  1. Connect a capable scan tool and verify U0249 and any other communication or network codes. Note whether the Rear B module is listed or absent on the network list.
  2. Check fuses and power/ground at the rear entertainment control module connector. Repair any blown fuses or poor grounds before further testing.
  3. Visually inspect module connector(s), wiring harnesses, and any in-line junctions/splices for damage, corrosion, or water intrusion. Repair or secure connectors as needed.
  4. With ignition ON, measure CAN High and CAN Low voltages at the module connector. Compare to expected values and check for a correct differential when the bus is active.
  5. With power OFF, measure resistance between CAN High and CAN Low at two points to confirm approximate 60 ohm termination. If missing or high, locate open/failed terminator or disconnected module.
  6. If physical layer checks pass but module is still not communicating, try swapping with a known-good identical module if available, or connect the suspected module to a bench harness to verify operation.
  7. Inspect for and disconnect any aftermarket devices or headrest units that interface with the rear entertainment network; retest network communication.
  8. If wiring and power are good and replacement module is available, program/configure the replacement per manufacturer procedures. Clear codes and confirm restoration of communication and functionality.
  9. If intermittent, perform wiggle tests on harnesses while monitoring network status and consider environmental tests (heat, moisture) where applicable.
  10. If diagnostics point to a vehicle network-wide issue (multiple missing nodes, bus-off), investigate other nodes, gateway module, and possible short to battery/ground on the bus.

Likely causes

  • Open or short in CAN High/CAN Low or LIN signal wiring to rear entertainment module
  • Lost power or poor ground at the rear entertainment module connector
  • Module has failed internally or is not configured/enabled on the vehicle network
  • Damaged connector or corrosion at the rear module or junction point
  • Bus termination resistor open or incorrect value (expected ~60 ohms total)

Fault status

⚠️ Status
Lost Communication With Entertainment Control Module - Rear B (U0249). Module not responding on vehicle data bus.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.5-3.0 hours

Similar codes

U0248 U0242 U0121 U0141 U0155 U1000
371

Browse 371 HYUNDAI manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

HYUNDAI

Your experience will help others
+100 karma for a short comment :)
Keep it short and practical. Up to 500 characters.
Send to email
Code

U0249

LAND ROVER U — Network/User

Lost communication with the rear control module entertainment B

Brand: LAND ROVER
Type: U — Network/User
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Faulty or missing rear entertainment control module (Rear B)
  • Power or ground supply fault to the module (blown fuse, poor ground, open power feed)
  • Damaged, shorted, or disconnected data bus wiring (CAN/LIN) or connectors
  • Failed or intermittent termination resistor on the communication bus
  • Corroded or water-damaged connector at the module or in-line splice
  • Aftermarket audio/video equipment or wiring modifications interfering with the network

Symptoms

  • Rear entertainment features inoperative (audio/video, rear screens, headphones)
  • Warning or message on instrument cluster about unavailable rear entertainment
  • Multiple related network communication codes present
  • Intermittent operation of rear entertainment or sporadic fault presence
  • Other modules reporting loss of a node on the network

What to check

  • Read all stored network and communication codes; note which modules are missing from the network scan tool list
  • Verify fuses and power feed to the rear entertainment control module are present and correct
  • Inspect module connectors and wiring for corrosion, damage, pin backout, or water intrusion
  • Measure key ground(s) for low resistance to chassis (verify good ground)
  • Check CAN bus physical layer: voltage at CAN High and CAN Low with ignition ON (idle ~2.5 V each), differential behavior when bus active
  • Measure total bus termination resistance (approx. 60 ohms between CAN High and CAN Low with power off)

Signal parameters

  • CAN High idle voltage: approx. 2.5 V (can vary 2.0–3.0 V depending on system)
  • CAN Low idle voltage: approx. 2.5 V (complementary to CAN High); differential idle near 0 V, active differential ~1–2 V
  • Expected bus termination: ~60 ohms between CAN High and CAN Low (two 120 ohm terminators in parallel)
  • Typical CAN bus speeds: 500 kbps or 250 kbps (verify factory spec for vehicle)
  • LIN bus: idle close to battery voltage when awake, signal toggles between near 0 V and battery voltage
  • Module supply voltage: close to battery voltage (12 V nominal) with ignition in required position

Diagnostic algorithm

  1. Connect a capable scan tool and verify U0249 and any other communication or network codes. Note whether the Rear B module is listed or absent on the network list.
  2. Check fuses and power/ground at the rear entertainment control module connector. Repair any blown fuses or poor grounds before further testing.
  3. Visually inspect module connector(s), wiring harnesses, and any in-line junctions/splices for damage, corrosion, or water intrusion. Repair or secure connectors as needed.
  4. With ignition ON, measure CAN High and CAN Low voltages at the module connector. Compare to expected values and check for a correct differential when the bus is active.
  5. With power OFF, measure resistance between CAN High and CAN Low at two points to confirm approximate 60 ohm termination. If missing or high, locate open/failed terminator or disconnected module.
  6. If physical layer checks pass but module is still not communicating, try swapping with a known-good identical module if available, or connect the suspected module to a bench harness to verify operation.
  7. Inspect for and disconnect any aftermarket devices or headrest units that interface with the rear entertainment network; retest network communication.
  8. If wiring and power are good and replacement module is available, program/configure the replacement per manufacturer procedures. Clear codes and confirm restoration of communication and functionality.
  9. If intermittent, perform wiggle tests on harnesses while monitoring network status and consider environmental tests (heat, moisture) where applicable.
  10. If diagnostics point to a vehicle network-wide issue (multiple missing nodes, bus-off), investigate other nodes, gateway module, and possible short to battery/ground on the bus.

Likely causes

  • Open or short in CAN High/CAN Low or LIN signal wiring to rear entertainment module
  • Lost power or poor ground at the rear entertainment module connector
  • Module has failed internally or is not configured/enabled on the vehicle network
  • Damaged connector or corrosion at the rear module or junction point
  • Bus termination resistor open or incorrect value (expected ~60 ohms total)

Fault status

⚠️ Status
Lost Communication With Entertainment Control Module - Rear B (U0249). Module not responding on vehicle data bus.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.5-3.0 hours

Similar codes

U0248 U0242 U0121 U0141 U0155 U1000
320

Browse 320 LAND ROVER manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

LAND ROVER

Your experience will help others
+100 karma for a short comment :)
Keep it short and practical. Up to 500 characters.
Send to email

Report

Harassment or bullying behavior
Contains mature or sensitive content
Contains misleading or false information
Contains abusive or derogatory content
Contains spam, fake content or potential malware

Block Member?

Please confirm you want to block this member.

You will no longer be able to:

  • See blocked member's posts
  • Mention this member in posts
  • Invite this member to groups
  • Message this member
  • Add this member as a connection

Please note: This action will also remove this member from your connections and send a report to the site admin. Please allow a few minutes for this process to complete.

Report

You have already reported this .